Just gonna repost something I posted on the bug thread on reddit:
Alright. I've tried everything and finally could be on to something with the freezes that happen every 15 mins or so.
My pc can handle Ultra at 60 fps (gtx 980). I changed the settings so it's locked to 30 fps. Since then, I've gone 1 hour and 40 mins without a freeze. In that time, I've done just random quests, rode around, killed monsters, and just did the griffin fight.
Another note: I didn't die at all in that time. Could be something to do with loading too. I alt tabbed a few times yesterday and it was showing a screen of an earlier save for some reason. EDIT: even with 30 fps lock and using driver 347.88, sometimes when I alt-tab it still shows an earlier screen of the game.
I'm using the nvidia driver that was before the GTA V one too. Haven't actually tried this driver at 60 fps, but all the other drivers I tried were at 60 fps and froze constantly.
Sucks to play on 30 when my PC can do 60, but for now it'll have to do. It could help Nvidia and CDprojekt narrow down the problem.